Our recent studies on the mechanism of HSV-2 induced transformation have shown that: (i) neoplastic transformation of normal diploid cells is mediated by the Bg1 II C fragment of HSV-2 DNA (0.416-0.580 map units), (ii) the transformation process involves at least two steps: cellular immortalization mediated by sequences within 0.410-0.525 map units, and the acquisition of neoplastic potential that requires sequences within 0.525-0.580 map units on the HSV-2 genome (presumptive neoplastic sequences), and (iii) the expression of a viral protein designated ICP 10 that is encoded within the presumptive neoplastic sequences correlates with the acquisition of anchorage independent growth and tumorigenic potential by HSV-2 transformed cells. The studies proposed in this application are designed to obtain a better understanding of the role played by the presumptive neoplastic sequences and the proteins that they encode, primarily ICP10, in neoplastic transformation. The specific aims are: (i)\to determine and compare the transforming activities of the subfragments of the presumed neoplastic sequences, in transforming activities of the subfragments of the presumed neoplastic sequences, in various combinations with immortalizing sequences and the sequences homologous to the various combinations with immortalizing sequences and the sequences homologous to the mammalian cell genome, (ii) to determine and compare the transforming activities (at 34 and 39 C) of the tsA8 mutant (in 130K and ICP 10 proteins) before and after marker rescue of the conditionally lethal function (in 130K), (iii) to inhibit ICP 10 synthesis with an oligonucleoside methylphosphonate complementary to the translation initiation region of the ICP 10 mRNA and determine the effect on transformation, (iv) to define and identify DNA sequences homologous to the presumptive neoplastic sequences in the transformed lines and their potential interaction with hamster cell DNA sequences and (v) to identify viral proteins in the transformed cells with particular emphasis on ICP 10, a protein that is encoded by the presumptive neoplastic sequences. These studies should provide a better understanding of the mechanism of HSV-2 induced neoplastic transformation.